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Video: Energy bubbles discovered at galaxy's heart

Scientists have detected two gigantic bubbles of high-energy radiation spilling out from the Milky Way's center that may have erupted from a supermassive black hole.

The mysterious structures each span 25,000 light-years across, and are emitting gamma rays, the highest-energy wavelength of light.

NASA/DOE/Fermi LAT/D. Finkbeiner et al.

A giant gamma-ray structure, resembling bubbles, has been discovered by processing Fermi space observatory all-sky observations. The dumbbell-shaped feature (center) emerges from the galactic center and extends 50 degrees north and south from the plane of the Milky Way, spanning the sky from the constellation Virgo to the constellation Grus.

The bulbous features may be evidence of a burst of star formation a few million years ago, researchers said. Or they may have been produced when a supermassive black hole in the center of our galaxy gobbled up a bunch of gas and dust.

"We don't fully understand their nature or origin," said study leader Doug Finkbeiner of the Harvard-Smithsonian Center for Astrophysics.

Scanning the gamma ray sky
Finkbeiner and his team used observations from NASA's Fermi Gamma-ray Space Telescope, which maps the sky's gamma-ray light. The scientists processed data from Fermi's Large Area Telescope, the highest-resolution gamma-ray detector ever launched.

By filtering out the fog of background gamma rays suffusing the sky, the researchers were able to pick out the huge bubbles. The scientists weren't flying blind; previous studies by other astronomers using other instruments had found intriguing clues that a huge, previously unknown structure might be lurking near the Milky Way's heart.

"We were definitely looking for something," Finkbeiner told reporters today (Nov. 9). "Some hints of this signal had been seen before, but not convincingly."

The two bubbles are dramatic, enigmatic and huge. They're emitting about the same amount of energy as 100,000 exploding stars, or supernovae, Finkbeiner said.

The structures extend as far as the distance between our solar system and the galaxy's core (the bubbles don't envelop Earth; they spread out in a different plane).

A paper about the findings will be published in an upcoming issue of The Astrophysical Journal.

Possible causesResearchers aren't yet sure what created the bubbles. But the structures appear to have sharp, well-defined edges, suggesting they were formed by a large, rapid and relatively recent release of energy.

Two leading candidate causes, according to Finkbeiner, are a surge of star formation several million years ago and a burst of activity by the Milky Way's central black hole, which is as massive as four million suns.

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